Checking your outgoing mail server (Is Port 25 blocked?)

Applies to: All Service Types

Difficulty: Medium

Time Needed: 20

Tools Required: SSH

Introduction

Many email clients and services use port 25 for SMTP to send out emails. However an ISP (Internet Service Provider) may block port 25 in order to prevent spamming by its customers. This article will show you how you can check to see if Port 25 is blocked on your network.

Before you start

This article assumes that you know how to get to a command prompt on your computer. If you need help with this, please see our KnowledgeBase article Using telnet.

READ ME FIRST

This article is provided as a courtesy. Installing, configuring, and troubleshooting third-party applications is outside the scope of support provided by Media Temple. Please take a moment to review the Statement of Support.

Instructions

Type the following command:

telnet example.com 25

View Results: If Port 25 is not blocked, you will get a successful 220 response (text may vary).

You can use this same technique to check if Port 587 is blocked as well. Just use the following command:

telnet example.com 587

FAQs

Q: What can I do if port 25 is blocked?A: You may also choose to use the alternate Port 587. All of our customers should contact their ISP (Internet Service Provider) if Port 25 is blocked. In many instances, they will let you use their outgoing SMTP servers.